Merger with DuPont (Details) - USD ($) $ / shares in Units, $ in Millions	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2017	Sep. 01, 2017	Aug. 31, 2017	Dec. 31, 2016
Planned Merger with DuPont [Line Items]
Common Stock, Par or Stated Value Per Share		$ 0.01			$ 2.50
Common Stock, Shares, Issued		100			1,242,794,836
Dow [Member]
Planned Merger with DuPont [Line Items]
Common Stock, Par or Stated Value Per Share				$ 2.50
Dow to DowDuPont Share Exchange Ratio for Common Shares				1
DowDuPont [Member]
Planned Merger with DuPont [Line Items]
Common Stock, Par or Stated Value Per Share			$ 0.01	$ 0.01
Common Stock, Shares, Issued			100
Treasury Stock [Member]
Planned Merger with DuPont [Line Items]
Stock Repurchased and Retired During Period, Value	$ 935
Common Stock [Member]
Planned Merger with DuPont [Line Items]
Stock Repurchased and Retired During Period, Value	3,107
Additional Paid-in Capital [Member]
Planned Merger with DuPont [Line Items]
Stock Repurchased and Retired During Period, Value	$ 2,172